Terminal bushing having impedance means associated therewith



1966 YOSHIMASA YONEZAWA ETAL TERMINAL BUSHING HAVING IMPEDANCE MEANSASSOCIATED THEREWITH Filed Sept. 30, 1964 INVENTORS WITNESSES mm mm 80 Mm .m 0 Oh .T i f mT ma Y United States Patent 3,287,531 TERMINAL BUSHINGHAVING IMPEDANCE MEANS ASSOCIATED THEREWITI-l Yoshimasa Yonezawa andToshio Tanabe, Kashlo, Takarazuka-shi, Japan, assignors to MitsubishiDenki Kabushiki Kaisha, Tokyo, Japan, a corporation of Japan Filed Sept.30, 1964, Ser. No. 400,477 Claims'priority, application Japan, Dec. 30,1963, 38/ 98,915 7 Claims. (Cl. 200-444) This invention relates toterminal bushings having impedance means associated therewith and, moreparticularly, to improved constructional features and simplifiedmounting arrangements therefor.

A general object of the present invention is the provision of animproved terminal bushing having an impedance means constituting anintegral component part thereof and of simplified construction.

Another object of the invention is the provision of an improvedterminal-bushing structure having impedance means associated with theinteriorly-extending end of the terminal bushingand, according to apreferred arrangement, constituting the interiorly-extending casingstructure of the terminal bushing.

Another object of the present invention is the provision of an improvedand simplified type of circuit-interrupting structure of the typeinvolving a live-tank structure, that is one in which the surroundingtank is at line voltage in the closed-circuit position of theinterrupter, and in which improved and simplified terminal-bushingstructures are associated therewith.

Another object of the present invention is the provision of an improvedterminal-bushing structure in which impedance means is associatedtherewith, and in which the compressive force exerted axially of theterminal-bushing structure is utilized to advantage for maintaining goodcontact between the terminal portions of the impedance structure.

Yet a further object of the present invention is the provision of animproved terminal-bushing structure having impedance means associatedtherewith in which provision is additionally supplied for accommodatingdifferential axial movement of the several parts encountered duringoperating conditions over a wide ambient temperature range.

An ancillary object of the present invention is the provision of animproved terminal-bushing structure having an associated resistancemeans taking the place of the usual interiorly-extending insulatingcasing structure.

Further objects and advantages will readily become apparent upon readingthe following specification, taken in conjunction with the drawings, inwhich:

FIGURE 1 is a vertical sectional view taken through a terminal bushingembodying features of the present invention;

FIG. 2 is a diagrammatic view of a high-voltage circuitinterruptingstructure having two breaks in series, with a resistance means shuntingone of the breaks for lowering the rate of rise of the recovery-voltagetransient;

FIG. 3 is a diagrammatic view, somewhat similar to FIG. 2, butillustrating an application of the novel terminal-bushing structure ofFIG. 1 utilized with the type of circuit-interrupting structure of FIG.2, the contact structure being illustrated in the closed-circuitposition; and,

FIG. 4 is a modified type of terminal-bushing structure incorporatingthe principles of the present invention.

Referring to the drawings, and more particularly to FIG. 1 thereof, itwill be noted that the reference numeral 1 generally designates aterminal bushing having an impedance means 2 associated therewith. Asshown, an insulating casing 3, preferably formed of a suitable ceramicmaterial for weather-proof purposes is provided, being clamped between aterminal structure 4 and an inwardlyextending flange portion 5 of amounting sleeve 6, in turn, constituting a portion of a tank structure7.

Extending axially through the terminal-bushing structure 1 is arod-shaped terminal stud 10 having a radially outwardly-extendingterminal-flange portion 11 associated therewith. At the upper end of theterminal stud 10, as viewed in FIG. 1, there is provided a threadedportion 12, having threaded thereon a nut 13, which provides adjustmentfor clamping pressure, as exerted by a compression spring 16. As shown,the compression spring 16 is interposed between the base 17 of acup-shaped portion 18 of the terminal structure 4 and a spring washer 20disposed immediately below the adjustable clamping nut 13. As a result,the compression spring 16 provides compressive force exerted axiallythrough the weather-proof casing 3 and the interiorly-disposed impedancemeans 2. The terminal stud 10, as is obvious, has tensile stress imposedthereon.

The resistance means 2 is preferably formed of a single cylindricalblock of silicon carbide or, for certain applications, the resistancemeans 2 may comprise a plurality of juxtaposed plates of sinteredsilicon carbide. Reference may be had to Pirani U.S. Patent 2,205,308,issued June 18, 1940, for a description of a suitable resistancematerial of silicon carbide, which may provide adequate current-carryingcapacity for the resistance means 2.

With further reference to FIG. 1, it will be noted that an aperture 11ais provided through the terminal-plate portion 11, whereby the medium,such as sulfur-hexafiuoride gas (SP may pass from the tank interior 30,through the aperture 11a and into the interior 31 of theterminal-bushing structure 1, so as to provide the neces sary dielectricstrength between the inwardly-extending portion 5a of the supportingflange portion 5 and the rodshaped terminal stud 10, which may be atdifferent voltage potentials, as more fully described hereinafter.

To accommodate differential longitudinal expansion between the severalcomponent parts of the terminal bushing 1 during operation of theterminal bushing 1 throughout a wide ambient temperature range, there isprovided a plurality of sliding contact fingers 40 associated with theterminal-cup structure 18,.which bear radially inwardly upon theexternal side surfaces of the axially-extending terminal stud 10. As aresult, good contacting engagement is provided between the externalterminal pad 50 and the inwardly-extending terminal stud 10.

With reference to FIG. 2 of the drawings, it will be noted that there isillustrated, somewhat diagrammatically, a high-voltage, high-power,circuit-interrupting structure 60 of the type having a live-tankstructure. As is well known by those skilled in the art, a live-tankstructure is one having a surrounding metallic tank which is at linevoltage in the closed-circuit position of the interrupter. With furtherreference to FIG. 2, it will be observed that there is provided twoserially-related breaks 61, 62, which are opened in sequence. Shuntingthe main break 61 is a resistance 70, which functions to lower the rateof rise of the recovery-voltage transient, and to improve the powerfactor of the circuit during an opening operation. As further well known'by those skilled in the art, upon the interruption of the areassociated with the main contact break 61, additionalsubsequently-opened seriallyconnected break means 62 is provided tointerrupt the residual-current arc, and to provide a final opendisconnecting gap in the circuit interrupter in the fully opencir-cuitposition thereof.

Reference may be had to U.S. Patent 2,970,198, issued January 31, 1961,to J. E. Schrarneck, and assigned to the assignee of the instantapplication, and for a general description of a compressed-gas typecircuit interrupter involving two breaks in series with a resistanceshunting one of the breaks, and in which sequential operation of the twobreaks is provided. In addition, reference may be had to US. patentapplication filed October 12, 1961, Serial No. 144,720, now US. Patent3,214,546, issued October 26, 1965, to Winthrop M. Leeds, entitledCircuit Interrupters, and assigned to the assignee of the instantapplication, for a further description of a typical type of live-tankhigh-voltage circuit-interrupting structure involving shuntingresistance means.

With reference to FIG. 3, it will be noted that there is provided anapplication of the terminal-bushing structure 1 of FIG. 1 in the type ofhigh-voltage, high-power circuit-interrupting structure illustrated inFIG. 2. In more detail, it will be noted that the shunting resistancemeans 70 of FIG. 2 is connected by a connection 80 to the tank structure81, and that automatically such a connection is provided by thecontacting engagement of the resistance means 2 (FIG. 1) with the tankflange portion 5. As a result, the terminal-bushing structure 1 of FIG.1 provides the desirable shunting impedance means '70, illustrated inFIG. 2, in a simplified and compact arrangement.

As will be obvious, the live-tank structures 81 of FIGS. 2 and 3 aresupported an adequate distance up in the air by insulating supportingcolumns 85, through which preferably extends operating means, not shown,arranged to provide a sequential operation of the series contacts 61,62. Also, as is obvious, the electrical circuit through the live-tankstructures of FIGS. 2 and 3 extend through a terminal bushing 90 to thedisconnecting contact 62, and through the main contact-structure 61through the terminal-bushing structure 1 to the other line connection LIt will be noted that there result considerable advantages by theterminal-bushing structure 1 of FIG. 1 incorporating the resistancemeans 2 as an interiorly-extending casing portion, and making contactingengagement directly with the surrounding tank structure 7. Among theseadvantages is the fact that the usual internal insulating casing iseliminated, the cylindrical resistance means 2 taking the place of suchpreviously-required internal casing structure. Moreover, the contactingforce required between the impedance means 2 and the tank structure 7 isautomatically provided by the compressive force exerted by thecompression spring 16. As a result, additional contacting force providedby a separate spring means is not necessary. Finally, where theterminal-bushing structure 1 is filled with air, or various gaseousfluids, such as SP gas under a pressure higher than that of atmosphericpressure, the clamping force exerted through the casing elements mayreadily be increased in a simplified manner, and also providingadditional contacting pressure between the resistance means 2 and itsconnected terminal portions 5, 11.

FIG. 4 illustrates a further modification of the invention, wherein acontacting sleeve 1(15 may surround an interiorlytelescopically-arranged tensile rod 106. It will be noted that there isno need for the interiorly-disposed tensile rod 106 to be made of a goodconducting material, inasmuch as the surrounding contacting sleeve 105will carry the entire current, which passes through the terminalbushingstructure 107. The other elements of the modified-type ofterminal-bushing structure 107 are analogous to those previouslydescribed in connection with the terminal-bushing structure 1 of FIG. 1and will, therefore, not be repeated. It will merely be noted that thetensile rod 106 may be formed of a cheap material adequate to withstandtensile stress, such as steel, since it has no current-carryingfunction.

From the foregoing description of the invention it will be apparent thatthere is provided a novel terminal-bushing structure 1, 107incorporating impedance means 2 which may assume the :form of acylindrically-shaped resistance block of, for example, sintered siliconcarbide. The impedance means 2 takes the place of the previouslyrequiredinternal insulating casing structure, and moreover has the advantage ofutilizing to advantage the usually-provided compressive force along theterminal-bushing elements to provide good contacting engagement betweenthe impedance means and its end contacting components.

Although there has been illustrated and described specific structures,it is to be clearly understood that the same were merely for the purposeof illustration, and that changes and modifications may readily be madetherein by those skilled in the art, without departing from the spiritand scope of the invention.

We claim as our invention:

1. A live-tank high-power circuit interrupter including a metallicenclosing tank structure and a pair of interiorly-extending terminalbushings, insulating supporting means for supporting said live-tank upin the air away from ground potential, main contact means andseriallyrelated disconnecting contact means disposed interiorly of saidlive metallic enclosing tank, operating means for opening said maincontact means and said serially-related disconnecting contact means insequence, impedance means shunting said main contact means and providinga continued current path following opening of the main contact means,one of the terminal bushings having exterior and interior casingelements on opposite sides of the tank structure, said interior casingelement being wholly composed of resistance material, and said interiorcasing element wholly providing said impedance means.

2. A live-tank high-power circuit interrupter including a metallicenclosing tank structure and a pair of interiorlyextending terminalbushings, insulating supporting means for supporting said live-tank upin the air away from ground potential, main contact means andserially-related disconnecting contact means disposed interiorly of saidlive metallic enclosing tank, operating means for opening said maincontact means and said serially-related disconnecting contact means insequence, impedance means shunting said main contact means and providinga continued current path following opening of the main contact means,one of said interiorly-extending terminal bushings utilizing saidimpedance as an interiorly-situated casing structure therefor, said oneof the terminal bushings having exterior and interior casing elements onopposite sides of the tank structure, said interior casing element beingwholly composed of resistance material, and said interior casing,element wholly providing said impedance means, and compression meansfor the elements of said one terminal bushing including anaxially-extending terminal stud in tension, whereby said compressionmeans imposes compressive contacting force between saidinteriorly-disposed impedance casing structure and the end terminalportions thereof.

3. A terminal-bushing structure including an insulating casing and animpedance casing, and means extending axially interiorly of saidterminal-bushing structure for exerting compressive force upon the saidtwo casings.

4. The combination of claim 3, wherein said terminalstud means includesa tension rod and a surrounding contact sleeve.

5. In combination, a terminal bushing having an externalweather-proofinsulating casing, an internal impedance casing, axiallyextending generally rod-shaped current-conducting means having aradially outwardly-extending contacting flange portion in juxtapositionrelative to the interiorly-extending end of said internal impedancecasing, and conducting flange supporting means interposed between saidinsulating casing and said internal impedance casing.

6. The combination of claim 5, wherein said generally rod-shapedcircuit-conducting means includes a tensile rod, an envelopingcurrent-conducting contact sleeve, and sliding contact fingers makingsliding contacting engagement with the outer surface of the contactsleeve.

'7. In combination, tank means including an apertured flange means, aterminal-bushing having an external terminal extending into said tankmeans through said apermeans including an axially-extending tensionmeans disposed Within said tubular current conducting means imposingcompressive stress on said insulating and resistance casing elements.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner.

1. A LIVE-TANK HIGH-POWER CIRCUIT INTERRUPTER INCLUDING A METALLICENCLOSING TANK STRUCTURE AND A PAIR OF INTERORLY-EXTENDING TERMINALBUSHINGS, INSULATING SUPPORTING MEANS FOR SUPPORTING SAID LIVE-TANK UPIN THE AIR AWAY FROM GROUND POTENTIAL, MAIN CONTACT MEANS ANDSERIALLYRELATED DISCONNECTING CONTACT MEANS DISPOSED INTERIORLY OF SAIDLIVE METALLIC ENCLOSING TANK, OPERATING MEANS FOR OPENING SAID MAINCONTACT MEANS AND SAID SERIALLY-RELATED DISCONNECTING CONTACT MEANS INSEQUENCE, IMPEDANCE MEANS SHUNTING SAID MAIN CONTACT MEANS AND PROVIDINGA CONTINUED CURRENT PATH FOLLOWING OPENING OF THE MAIN CONTACT MEANS,ONE OF THE TERMINAL BUSHINGS HAVING EXTERIOR AND INTERIOR CASINGELEMENTS ON OPPOSITE SIDES OF THE TANK STRUCTURE, SAID INTERIOR CASINGELEMENT BEING WHOLLY COMPOSED OF RESISTANCE MATERIAL, AND SAID INTERIORCASING ELEMENT WHOLLY PROVIDING SAID IMPEDANCE MEANS.